As an ESD protection device, a silicon controlled rectifier (SCR) has an electrostatic discharge ability higher than, generally 5˜7 times higher than, that of a metal oxide semiconductor field effect transistor (MOSFET). FIG. 1 shows a schematic diagram of the cross-sectional structure of an existing high trigger voltage silicon controlled rectifier, wherein a collector of a parasitic PNP transistor composed of P+ region/high-voltage N-well/high-voltage P-well acts as a base of a parasitic NPN transistor composed of N+ region/high-voltage P-well/high-voltage N-well; similarly, a collector of the parasitic NPN transistor composed of N+ region/high-voltage P-well/high-voltage N-well also acts as a base of the parasitic PNP transistor composed of P+ region/high-voltage N-well/high-voltage P-well. FIG. 2 shows an equivalent circuit composed of the parasitic NPN and PNP transistors in FIG. 1. As shown in FIG. 1 and FIG. 2, a trigger voltage of a silicon controlled rectifier composed of the parasitic PNP transistor composed of P+ region/high-voltage N-well/high-voltage P-well and the parasitic NPN transistor composed of N+ region/high-voltage P-well/high-voltage N-well is a reverse breakdown voltage of a high-voltage N-well/high-voltage P-well junction. Generally, the reverse breakdown voltage of the high-voltage N-well/high-voltage P-well junction is high, therefore, the application of this structure is greatly limited. In addition, the parasitic NPN and PNP transistors gain positive feedbacks from each other to realize current amplification after the silicon controlled rectifier is switched on. Which leads to a low on-resistance, a large amplification and a low sustaining voltage after snapback occurs, generally from 2˜5 V. A normal working voltage of a high-voltage circuit could be much higher than such a sustaining voltage, therefore, using a silicon controlled rectifier as a high-voltage ESD protection circuit is easy to cause latch-up which is hard to be recovered.